PROJECT SUMMARY/ABSTRACT Most children with autism spectrum disorder (ASD) also have below-age vocabulary knowledge. These deficits are linked to their poor social communication skills. Vocabulary knowledge in the preschool years is a powerful predictor of outcomes. It is therefore crucial to understand how preschoolers with ASD can acquire new vocabulary. In the current proposal, we study how preschoolers with ASD and typically-developing (TD) children learn vocabulary in situations that place minimal demands on social communication skills to see if these can provide an alternate avenue for vocabulary instruction. Specifically, we study whether children can learn new words in overhearing contexts in which they are not directly addressed, but instead are witnesses to a conversation between two adults, one of whom introduces a new word to the other. Prior work has shown that TD children can learn new words in such situations, and there is preliminary evidence from the PI?s; work that children with ASD can as well. We also examine whether children can learn from these interactions when they take place on video, and whether they can acquire verbs and pronouns as well as nouns from these interactions. This research will shed light on the mechanisms underlying language learning in ASD and in TD and will support the development of effective language interventions.